1. Field of the Invention
The present invention relates to admixture composition for mixing with a lubricant that is used for various purposes.
2. Description of the Related Art
Admixture composition for improving the performances of lubricants by being mixed with lubricants that are used for various purposes such as in internal combustion engine oils, automatic transmission fluids (ATF), hydraulic oils in an airline industry, shock absorber oils and the like, to achieve a hydrodynamic nature of the resultant lubricants as a non-Newtonian elastic fluid, are proposed in U.S. Pat. No. 4,788,362. In U.S. Pat. No. 4,788,362, it is proposed that an admixture composition comprising an oil solution of polyisobutylene and an oil solution of an olefin copolymer or polymethacrylate. The oil solution of polyisobutylene contains polyisobutylene having a viscosity average molecular weight of 350,000-2,100,000 at a concentration in the range of 10 weight % to 90 weight %. When the admixture composition mixes with a lubricant, the oil solution of polyisobutylene mixes with the lubricant at a concentration in the range of 10 weight % to 90 weight %. The oil solution of an olefin copolymer or polymethacrylate is a viscosity index improver.
Mixing such admixture composition as those in U.S. Pat. No. 4,788,362 into the lubricants provides advantageous effects such as efficient fuel consumption in internal combustion engines such as those in automobiles, prevention of sticking, clarification of exhaust gas, decrease in abrasion, decrease in deterioration of the lubricant, i.e., extended durability of the lubricant which leads to a reduction in lubricant consumption and extended durability in the engine and so on. Further, the advantageous effects such as decrease in abrasion and reduction of fuel cost and power cost and so on are provided if the lubricants, with which such admixture composition are mixed, are used as operation fluids, gear fluids, general machine fluids and so on.
A variety of advantageous effects associated with environmental protection such as clarification of exhaust gas and reduction of waste oils or waste materials and so on are obtained by mixing the admixture composition of U.S. Pat. No. 4,788,362 with the lubricants. However, in the situation of the increasingly tight regulations related to environmental protection that has arisen in recent years, it is desired that the advantageous effects obtained by mixing the admixture composition of U.S. Pat. No. 4,788,362 with the lubricants are capable of being maintained for longer.
Deterioration of the admixture composition involves deterioration of the above-mentioned various advantageous effects obtained by mixing the admixture composition of U.S. Pat. No. 4,788,362 with lubricants. And, the deterioration of the admixture composition mainly occurs by mechanical shearing which is applied to the admixture composition. Therefore, it is necessary to improve the durability of the admixture composition against mechanical shearing, in order to maintain the advantageous effects obtained by mixing the admixture composition of U.S. Pat. No. 4,788,362 to lubricants for a longer term.
An object of the present invention is to improve the durability of the admixture composition against mechanical shearing.
A admixture composition for mixing with a lubricant of the present invention provides a solution to the above-indicated object by comprising an oil solution of polyisobutylene and an oil solution of star divinylbenzene-isoprene copolymer hydride. The oil solution of polyisobutylene contains polyisobutylene having a viscosity average molecular weight in a range of 350,000 to 2,100,000 at a concentration in the range of 10 weight % to 90 weight % and the oil solution of star divinylbenzene-isoprene copolymer hydride contains star divinylbenzene-isoprene copolymer hydride having a viscosity average molecular weight in a range of 200,000 to 800,000 at a concentration in the range from 3 weight % to 90 weight %. When the admixture composition mixes with a lubricant, the oil solution of polyisobutylene mixes with a lubricant at a concentration in the range from 10 weight % to 90 weight % and the oil solution of star divinylbenzene-isoprene copolymer hydride mixes with the lubricant at a concentration in the range of 3 weight % to 90 weight %. The oil solution of star divinylbenzene-isoprene copolymer hydride being a viscosity index improver
The deterioration of the admixture composition is mainly involved the deterioration of the viscosity index improver. More specifically, the viscosity index improver deteriorates by being applied with a mechanical shearing action to become impossible to prevent a change in the viscosity of the admixture composition, thereby leading to the deterioration of the admixture composition. In this way, the admixture composition of the present invention can improve the durability of the viscosity index improver against the mechanical shearing by employing star divinylbenzene-isoprene copolymer hydride as a viscosity index improver.
Moreover, even though the durability of the viscosity index improver against the mechanical shearing can be improved by employing star divinylbenzene-isoprene copolymer hydride, it is not desirable if the performances of the present admixture composition become worse than ones of the admixture composition of U.S. Pat. No. 4,788,362, since the various advantageous effects, that are obtained by mixing the admixture composition of U.S. Pat. No. 4,788,362 to lubricants, may not be obtained. Thus, in addition to comprising an oil solution of polyisobutylene, which contains polyisobutylene having a viscosity average molecular weight in a range of 350,000 to 2,100,000 at a concentration in the range of 10 weight % to 90 weight %, the present invention provides comprising an oil solution of star divinylbenzene-isoprene copolymer hydride, which contains star divinylbenzene-isoprene copolymer hydride having a viscosity average molecular weight in a range of 200,000 to 800,000 at a concentration in the range of 3 weight to 90 weight %, thereby preventing that the performances of the admixture composition becomes worse than ones of the admixture composition of U.S. Pat. No. 4,788,362. Also, when the admixture composition mixes with a lubricant, the oil solution of polyisobutylene mixes with a lubricant at a concentration in the range of 10 weight % to 90 weight % and the oil solution of star divinylbenzene-isoprene copolymer hydride mixes with the lubricant at a concentration in the range of 3 weight % to 90 weight %.
Therefore, the admixture composition of the present invention improves the durability of the admixture composition against the mechanical shearing, by employing the above-mentioned constitution.
Further, the star divinylbenzene-isoprene copolymer hydride of the present invention may have a viscosity average molecular weight within a range of 400,000 to 650,000. In this constitution, the effects as the viscosity index improver and the necessary fluidity can be more surely obtainable, and thus this is preferable.